Most adults in the U.S. will be overweight or obese by 2030, with related health care spending projected to be as much as $956.9 billion, according to researchers at the Johns Hopkins Bloomberg School of Public Health, the Agency for Healthcare Research and Quality (AHRQ), and the University of Pennsylvania School of Medicine.

Their results are published in the July 2008 online issue of Obesity.

"National survey data show that the prevalence of overweight and obese adults in the U.S. has increased steadily over the past three decades," said Youfa Wang, MD, PhD, lead author of the study and associate professor with the Bloomberg School's Center for Human Nutrition.

"If these trends continue, more than 86 percent of adults will be overweight or obese by 2030 with approximately 96 percent of non-Hispanic black women and 91 percent of Mexican-American men affected. This would result in 1 of every 6 health care dollars spent in total direct health care costs paying for overweight and obesity-related costs," Wang added.

The researchers conducted projection analyses based on data collected over the past three decades from nationally representative surveys. Their projections illustrate the potential burden of the U.S. obesity epidemic if current trends continue.

"Our analysis also shows that over time heavy Americans become heavier," according to May A. Beydoun, a former postdoctoral research fellow at the Johns Hopkins Bloomberg School of Public Health.

"The health care costs attributable to obesity and overweight are expected to more than double every decade. This would account for 15 to 17 percent of total health care costs spent," Wang said. "Due to the assumptions we made and the limitations of the available data, these figures are likely an underestimation of the true financial impact."

Current standards define adults with a body mass index (BMI) between 25 and 29.9 as overweight and adults with a BMI of 30 or higher as obese. Both the overweight and obese are at an increased risk for developing a number of health conditions, including hypertension, type 2 diabetes, heart disease and stroke. Researchers estimate that children and young adults may have a shorter life expectancy than their parents if the obesity epidemic is left unaddressed.

The authors warned that obesity has become a public health crisis in the U.S. Timely, dramatic and effective development and implementation of corrective programs and policies are needed to avoid the otherwise inevitable health and societal consequences implied by their projections.

If current trends continue, the researchers warn that the U.S. Department of Health and Human Services will not meet its Healthy People 2010 initiative to increase the proportion of adults who are at a healthy weight and to reduce the proportion of adults who are obese.

More exercise recommended for weight loss

In addition to limiting calories, overweight and obese women may need to exercise 55 minutes a day for five days per week to sustain a weight loss of 10 percent over two years. That's the conclusion of researchers writing in the latest issue of Archives of Internal Medicine, one of the JAMA/Archives journals.

More than 65 percent of U.S. adults are overweight, a public health concern, according to background information in the article.

"Among obese adults, long-term weight loss and prevention of weight regain have been less than desired," the authors write. "Therefore, there is a need for more effective interventions."

Current recommendations prescribe 30 minutes of moderate physical activity on most days of the week, for a total of 150 minutes per week. However, a growing consensus suggests that more exercise may be needed to enhance long-term weight loss.

To calculate the amount of exercise needed, John M. Jakicic, Ph.D., of the University of Pittsburgh, and colleagues enrolled 201 overweight and obese women in a weight loss intervention between 1999 and 2003. All the women were told to eat between 1,200 and 1,500 calories per day. They were then assigned to one of four groups based on physical activity amount, burning 1,000 calories vs. 2,000 calories per week, and intensity. Group meetings focusing on strategies for modifying eating and exercise habits, as well telephone calls with the intervention team, also were conducted over the two-year period.

After six months, women in all four groups had lost an average of 8 percent to 10 percent of their initial body weight. However, most were not able to sustain this weight loss. After two years the women's weight was an average of 5 percent lower than their initial weight, with no difference between groups.

The 24.6 percent of individuals who did maintain a loss of 10 percent or more over two years reported performing more physical activity than those who lost less weight. They also completed more telephone calls with the intervention team, engaged in more eating behaviors recommended for weight control and had a lower intake of dietary fat.

"This clarifies the amount of physical activity that should be targeted for achieving and sustaining this magnitude of weight loss, but also demonstrates the difficulty of sustaining this level of physical activity," the authors wrote. "Research is needed to improve long-term compliance with this targeted level of physical activity. Moreover, continued contact with the intervention staff and the ability to sustain recommended eating behaviors also may be important contributing factors to maintaining a significant weight loss that exceeds 10 percent of initial body weight, which suggests that physical activity does not function independently of these other behaviors.